Lac repressor protein (LacI)

The Lac repressor protein (LacI) is a DNA-binding transcriptional repressor found in bacteria such as Escherichia coli. It controls the expression of genes required for the metabolism of lactose (the lac operon) by binding specifically to the operator sequence of the operon and blocking transcription. In the absence of lactose, LacI binds tightly to the operator DNA, preventing RNA polymerase from transcribing lactose-utilizing genes. When lactose is present, some is converted to allolactose, which acts as an inducer by binding to the repressor and causing a conformational change that reduces its affinity for DNA. This releases the repressor from the operator, allowing transcription of genes necessary for lactose uptake and metabolism. The lac repressor is a homotetrameric protein with distinct DNA-binding and regulatory domains, and is a famous model for studying genetic regulation, allostery, and protein-DNA interaction, but it is not a direct therapeutic or diagnostic target[1][2][4][5][6].

Other names

LacILactose repressor proteinLac repressorLactose operon repressorLac repressor protein (E. coli)

Allosteric inhibition (binding of allolactose or IPTG induces a conformational change that decreases DNA binding affinity, lifting repression of the lac operon)